There is a known ink jet printer including a plurality of channels adapted to eject ink and adapted to output a two-dimensional image by controlling ink ejection while moving relative to a recording medium such as paper or cloth. For an ink ejection method, there are known methods of, for example, a pressure type by various actuators such as a piezoelectric actuator, an electrostatic actuator, or an actuator utilizing thermal deformation, a thermal type that generates bubbles by heat, and the like.
A liquid ejection head included in the above-described ink jet printer has a structure in which ink supplied from an ink supply source is distributed to each pressure chamber from a common chamber and then reaches an ejection port. When the pressure chamber is pressurized by an actuator or the like, the ink is ejected from the ejection port. Pressure waves generated at the time of pressurizing the pressure chamber pass through the common chamber and propagate to another pressure chamber communicating with the common chamber, and pressure fluctuation is induced in the pressure chamber. In the case where such pressure fluctuation is induced, ink ejection characteristics in the pressure chamber may be changed and ejection failure may occur.
To prevent such ejection failure, it may be possible to exemplify patent literature such as JP 2006-95725 A (Patent Literature 1), JP 2006-198903 A (Patent Literature 2), and JP 2007-313761 A (Patent Literature 3) disclosing a liquid ejection head including a damper portion that attenuates pressure waves propagating to a common chamber.
According to the liquid ejection head disclosed in Patent Literature 1, a recess portion is provided in a reinforcing plate located outside a wall portion such that a part of the wall portion defining a common chamber can be warped and deformed outward. According to the liquid ejection head disclosed in Patent Literature 2, a part of a wall portion defining a common chamber is formed of a flexible ink plate.
According to the liquid ejection head disclosed in Patent Literature 3, a part of a wall portion defining a common chamber is formed in a deformable manner and a viscoelastic material is provided in a manner contacting this deformable portion.
However, even in the case where pressure waves propagating to the common chamber are attenuated as disclosed in Patent Literatures 1 to 3, bubbles may be generated due to cavitation because a pressure inside a pressure chamber becomes negative after ink is ejected from an ejection port. Specifically, in the case where the pressure inside the pressure chamber becomes lower than a saturated vapor pressure of the ink, nuclei of fine bubbles are generated and the nuclei grow into bubbles. When such bubbles exist in the pressure chamber, the ink may not be able to be ejected from the ejection port due to nozzle clogging or pressure loss. Consequently, image failure may be caused.
On the other hand, according to JP 7-304171 A (Patent Literature 4), a thin layer made of a material having an elastic coefficient lower than that of a piezoelectric material constituting an actuator plate is formed on a part of a wall of an ink liquid chamber corresponding to the above-described pressure chamber so as to attenuate a peak of a negative pressure after ink ejection.